sub boxes

is it a bad thing to have an undersized sub box?
I built a box for a 12" bazooka sub and just upgraded to a 12" memphis... The way i have it all set up its a real pain to make another box that is bigger... I only needed .87 cu. ft. before but now i need a full cubic foot. So is it really that bad to just use an undersized sub box?

really i just need to know if a box that is too small will affect quality or volume, or more importantly will it cause any damage to the sub. (Its a sealed box, not ported or vented)

[lee]

a too small sealed box produces some loss in sound quality becuase it makes a "hump" in the lower end of the bass response (and usually a faster roll off). Some people actually like this as it makes the bass sound like it has more punch. It will not damage the woofer - too large a box might, but not too small. If you tell me the model I should be able to produce a couple of graphs showing the outputs for comparison.

i have a memphis MC-124D

What kind of sound is produced in the "hump"?

I'm trying really hard to get the best possible sound quality with this system; so do you suggest that i rebuild the box? would a .13 cu ft make a noticable difference?

[lee]

the difference between those two size boxes would be small enough most ears could not hear it. for what is termed "flat" response the box size models out to 3.3 cu ft. I've attached a graph showing spl by frequency for 200 watts RMS input. the two lines close to each other are the two size boxes you mention. The smaller box (what you have) has the slightly higher hump and slightly faster roll off in the low end. The other curve is the 3.3 cu ft curve. It seems Memphis puts out specs for a punchy sound anyway. The Thiele/Small paramaters plugged into my modeling program is what suggested a 3.3 cu ft sealed box. let me know if this makes sense.

[SubaSteevo]

I'm gonna hop in and ask a question too.

I got a used 12" Infiniti Reference 1210 of ebay to replace my Pioneer 12" that died on me. The Infiniti came with the box pictured on the left. The box on the right is a walmart box I had from the Pioneer. Their interior dimensions are similar (the new one is slightly larger), so what difference would the shape of the box make?

[lee]

Originally posted by BurgundyBeast
snip.... so what difference would the shape of the box make?

For a sealed box - for all practical purposes (car audio), none - except if the box was too shallow, i.e., the back of the magnet had less than say 1/2" clearance to the wood.

[SubaSteevo]

Originally posted by lee


For a sealed box - for all practical purposes (car audio), none - except if the box was too shallow, i.e., the back of the magnet had less than say 1/2" clearance to the wood.

Thanks!

Originally posted by lee
th let me know if this makes sense.

ok.... i think so;

basically this means that frequencies around 50 to 100 hz will be slightly louder than what they shoud be??

but you think that the difference between a 1 cu ft box and a .87 cu ft box isnt really noticable... and I dont think i really have enough room for a 3.3 cu ft box. thanks a lot for all your help.

[lee]

Originally posted by simonton
basically this means that frequencies around 50 to 100 hz will be slightly louder than what they shoud be??

but you think that the difference between a 1 cu ft box and a .87 cu ft box isnt really noticable... and I dont think i really have enough room for a 3.3 cu ft box. thanks a lot for all your help.

Correct on size - you won't be able to tell the diff between 1 and 0.87.

However, the issue is not so much louder than they should be, but less tonally balanced. HOWEVER, for car audio there's this phenomenon involving bass amplification at certain frequencies sometimes known as the transfer function (if I remember terms correctly - always suspect at my advanced age). Until someone gets ambitious and measures it I (and no one else) can really say which graph/response is better for the SVX. The function involves size of the car (smaller is better for amplification) and a complex function of shape and sound damping materials used in the interior. Here's the basic method should someone want to try. Buy a SPL meter. Find a quiet, but open space. Measure the volume inside the car (windows up) at various bass frequencies, say every 5 Hz from 20 to 100. Take the box outside and measure the same thing again. You will note lower volumes outside, subtract one from the other and voila, you would know how large to make the box (hint: have the curve fall off at the same rate as it rises when in-car).

I have such a SPL meter, I'm just a) lazy, b) don't care enough, c) have too many "honey-do's, or d) all the above.

[drivemusicnow]

OOoohhh OOOooohhh D! i Win... however you definitly won this thread